Operates great through phone line, radios, or scanners. The SWEET 16 TONE DECODER detects DTMF "Dual Tone Multi-Frequency" data (those sounds you hear when pushing buttons on your phone), and - when each button is pressed it sends a unique voltage to the electronics on the printed circuit board which turns a circuit on or off. There are 16 different touch tones, 12 of which are on a normal phone; special key pads have 4 additional buttons (A, B, C, D). This decoder gives an output voltage for all 16 touch tones. The Sweet 16 Tone Decoder has on the printed circuit board one (1) relay and driver circuit. If you want to use all 16 you can build your own board with 16 relays and driver circuits on it, or to get fancier use a flip-flop IC to achieve a "toggle" effect (push ON, push OFF), or a 555-timer to provide a timing effect (on for 5 minutes, then off) - the choices are almost unlimited. Any one output may be connected to the onboard relay circuit.